When manufacturing semiconductor devices, it is common to utilize techniques requiring a high degree of precision. For example, the chemical vapor deposition (CVD) method used in manufacturing integrated circuits involves deposition of precise quantities of materials such as SiH.sub.4 and WF.sub.6 in precise ratios. In order to ensure that proper deposition is achieved, it is mandatory to use one or more calibrated MFCs to regulate such gas flows.
The mass flow controllers commonly used have five active dc voltage levels that must be monitored so that the MFCs can be properly calibrated within the necessary tolerance ranges. For example, the set point voltage and the flow voltage on each MFC must be monitored so as to maintain the desired deposition and ratio levels. These voltages must be measured with a sufficient degree of accuracy so that they may be compared in order to determine whether an MFC is operating properly or requires calibration.
Previous monitoring techniques experience various drawbacks. For example, according to at least one prior art monitoring technique, MFC voltage levels are monitored with a control device which also controls other functions of the MFC. Using such a device, the operator cannot control other functions of the system (e.g., a Genus system) while monitoring is being performed.